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Configuring Spanning Tree Parameters
Configuring Port Connection Type
Specifying a port connection type is done when using the Rapid Spanning Tree Algorithm and Protocol
(RSTP), as defined in the IEEE 802.1w standard. RSTP transitions a port from a blocking state directly to
forwarding, bypassing the listening and learning states, to provide a rapid reconfiguration of the Spanning
Tree in the event of a path or root bridge failure. Rapid transition of a port state depends on the
configurable connection type of the port. These types are defined as follows:
•
Point-to-point LAN segment (port connects directly to another switch).
•
No point-to-point shared media LAN segment (port connects to multiple switches).
•
Edge port (port is at the edge of a bridged LAN, does not receive BPDU and has only one MAC
address learned). Edge ports, however, will operationally revert to a point to point or a no point to
point connection type if a BPDU is received on the port.
A port is considered connected to a point-to-point LAN segment if the port belongs to a link aggregate of
ports, or if auto negotiation determines if the port must run in full duplex mode, or if full duplex mode was
administratively set. Otherwise, that port is considered connected to a no point-to-point LAN segment.
Rapid transition of a designated port to forwarding can only occur if the port connection type is defined as
a point to point or an edge port. Defining a port connection type as a point to point or as an edge port
makes the port eligible for rapid transition, regardless of what actually connects to the port. However, an
alternate port is always allowed to transition to the role of root port regardless of the alternate port
connection type.
Note. Configure ports that will connect to a host (PC, workstation, server, etc.) as edge ports so that these
ports will transition directly to a forwarding state and not trigger an unwanted topology change when a
device is connected to the port. If a port is configured as a point to point or no point to point connection
type, the switch will assume a topology change when this port goes active and will flush and relearn all
learned MAC addresses for the port's assigned VLAN.
If the switch is running in the per-VLAN Spanning Tree mode, then the connection type applies to the
specified VLAN instance associated with the port. If the switch is running in the flat Spanning Tree mode,
then the connection type applies across all VLANs associated with the port. The flat mode instance is
referenced as the port instance, even if the port is associated with other VLANs.
By default, Spanning Tree is automatically enabled on the port, the connection type is set to auto point-to-
point, and auto edge port detection is enabled. The auto point-to-point setting determines the connection
type based on the operational status of the port. The auto edge port setting determines the operational edge
port status for the port.
The
spantree vlan connection
connection type for a VLAN instance or the CIST instance. See
page 5-42
for information about configuring the auto edge port status for a port.
To change the port connection type for a VLAN instance regardless of which mode (per-VLAN or flat) is
active for the switch, use the spantree vlan connection command. For example, the following command
defines the connection type for port 8/1 associated with VLAN 10.
-> spantree vlan 10 port 8/1 connection autoptp
OmniSwitch AOS Release 7 Network Configuration Guide
and
spantree cist connection
March 2011
Configuring STP Port Parameters
commands are used to configure the port
"Configuring the Edge Port Status" on
page 5-41
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